Device and method for additive casting of metallic parts

ABSTRACT

A method and an apparatus for additive casting of parts is disclosed. The method may include: depositing, on a build table, a first portion of a mold, such that, the depositing may be performed layer by layer; pouring liquid substance into the first portion of the mold to form a first casted layer; solidifying at least a portion of the first casted layer; depositing a second portion of the mold, on top of the first portion of the mold; pouring the liquid substance into the second portion of the mold to form a second casted layer, on top of at least a portion of the first casted layer; and solidifying at least a portion of the second casted layer. The method may further include joining the first and second casted layers prior to the pouring of a third casted layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation in Part Application of PCTInternational Application No. PCT/IL2018/051006, International FilingDate Sep. 6, 2018, claiming the benefit of U.S. Patent Application No.62/557,167, filed Sep. 12, 2017, which are hereby incorporated byreference.

TECHNICAL FIELD OF THE INVENTION

The application generally relates to the field of casting parts. Morespecifically the application relates to the field of additive casting ofparts.

BACKGROUND OF THE INVENTION

Casting is one of the oldest material-forming methods still used today.The idea of pouring liquid material into a mold which contains a hollowcavity of the desired shape and then allowed it to solidify is 6000years old. The principal process has not changed since 3200 BC whenbronze was melted and poured into a stone mold. When glass was inventedaround 3000 years ago, glass was also casted in molds (in addition tothe glass blowing process) in order to form articles made from glass. Inmodern days, polymer resins are also casted into molds in order to formshaped polymeric parts.

Modern casting methods involve the use of molds made from variousmaterials, such as sand casting, die casting (e.g., a metallic mold),semi-die casting (e.g., metallic mold and sand inserts), investmentcasting (e.g., a ceramic shell mold), lost foam casting (e.g., relapsingpolymeric foam with molten metal placed in a sand container) and thelike. However, the idea of pouring all the required amount of metal inorder to form a desired object/part at a single pouring act has notchanged.

Casting, although being a very reliable method, is also very expensive,time consuming, and is adapted for large production quantities. The timerequired in order to form the molds of die casting or make a mold forsand casting molds is typically several months. Furthermore, even themost modern casting methods are not flexible to changes. Every littlechange to the mold makes the process more expensive and delays theproduction time.

Printing three-dimensional (3D) objects is one of the newestmaterial-forming methods. Inks made from polymer resins, metallicpowders mixed with binders or ceramic powders mixed with binders areprinted on a build table, sometimes with the addition of a printedshell/support structure to support the printed object. A 3D computerizedmodel is used to create the printed object. Accordingly, any change inthe 3D model is easily implemented without the need to change any of theprinting parameters. However, the quality of the printed part, (forexample, mechanical properties, material defects, voids anddislocations) in particular metal printed parts that further requireheat treatment processes are often inferior to the quality of castedparts.

Currently used processes for three-dimensional printing of metal objectsincludes deposition of metal powder/particles, layer by layer, followedby a selective laser sintering (SLS) to melt/solidify the fine depositedlayer. Another process includes printing a wax pattern of the mold by athree-dimensional printer, for subsequent use in an investment castingto fabricate a metal object. However, because the three-dimensionalprinting results are the fabrication of the mold rather than thefinished metal object itself, additional stages of gravitational castingare required in order to finish the metal object.

Therefore, there is a need for a system and a method that obviate thedisadvantages of the above production methods.

SUMMARY OF THE INVENTION

Some aspects of the invention may be directed to a method of additivecasting of parts. In some embodiments, the method may include:depositing, on a build table, a first portion of a mold, such that, thedepositing is performed layer by layer; pouring liquid substance intothe first portion of the mold to form a first casted layer; solidifyingat least a portion of the first casted layer; depositing a secondportion of the mold, on top of the first portion of the mold; pouringthe liquid substance into the second portion of the mold to form asecond casted layer, on top of at least a portion of the first castedlayer; and solidifying at least a portion of the second casted layer.

In some embodiments, the method may further include receiving athree-dimensional (3D) part model including one or more parts, the partmodel is divided into a plurality of casted layers. In some embodiments,the method may further include receiving a 3D mold model, the mold modelis divided into a plurality of mold portions, wherein the mold model isdesigned to provide a desired shape to the liquid substance. In someembodiments, the method may further include generating a 3D mold modelbased on the received part model, the mold model is divided into aplurality of mold portions, wherein the mold model is designed toprovide a designed shape to a liquid substance.

In some embodiments, the liquid substance is one of: a molten metal, amolten glass and a polymer resin. In some embodiments, the method mayfurther include joining the first and second casted layers prior to thepouring of a third casted layer. In some embodiments, joining mayinclude melting at least a portion of the interface between the firstand second casted layers. In some embodiments, joining may includetreating at least a portion of an upper surface of the second castedlayer with at least one of: an induction heater, a resistance welder, anultrasonic welder, plasma deposition unit, E-beam, a laser, a weldingarc, a torch, cold fusion and magnetic field flow. In some embodiments,joining may include at least one of: gluing, ultrasonic bonding,diffusion bonding, heat curing and ultraviolet (UV) curing.

In some embodiments, the method may further include pre-heating eachcasted layer prior to the pouring of an additional casted layer. In someembodiments, the method may further include providing surface treatmentto each casted layer after solidification and prior to the pouring of anadditional casted layer. In some embodiments, the surface treatment mayinclude at least one of: machining, grinding, polishing and laserablation. In some embodiments, the method may further include: providingsurface treatment to internal walls of each mold portion prior to thepouring of the corresponding casted layer. In some embodiments, thesurface treatment to internal walls of each mold portion may includemachining the internal walls and removing the excess material.

In some embodiments, the method may further include leveling the firstcasted layer and the first mold portion to be in the same level prior tothe deposition of the second mold portion. In some embodiments, thedepositing and pouring steps are performed under a protectiveatmosphere. In some embodiments, the first and second casting layershave different thicknesses. In some embodiments, the first and secondcasted layers have thickness of between 0.1-12 mm. In some embodiments,each mold layer may include a mixture of granular material and a binder,wherein the granular material may include at least one of: ceramicpowders, sand, clay, and any combination thereof. In some embodiments,the mixture may further include metallic powder.

In some embodiments, depositing the one or more mold layers may includeprinting each mold layer using a 3D printer. In some embodiments,pouring the liquid substance is from a movable pouring unit including atleast one liquid introduction port for pouring liquid substance. In someembodiments, the movable pouring unit may be configured to pour apredetermined amount of liquid substance at predetermined locations ineach mold portion. In some embodiments, the method may further includeannealing the solidified first casted layer by pouring molten metal toform a third and a fourth casted layers. In some embodiments, the firstcasted layer is casted by pouring a first liquid substance having afirst chemical composition; and the second casted layer is casted bypouring a second liquid substance having a second chemical composition.In some embodiments, the first liquid substance and the second liquidsubstance may be selected from: two alloys of the same metallic element,two types of glass and two types of polymers.

In some embodiments, the first liquid substance and the second liquidsubstance differ in at least one of: the amount and the type ofadditives, wherein the additives are configured to at least: evaporateand decompose during casting. In some embodiments, the method mayfurther include: measuring a chemical composition of the liquidsubstance in the first container prior to pouring the liquid substanceinto at least one of: the first mold portion and the second moldportion; measuring the chemical composition of the corresponding castedlayer; and comparing the measurements. In some embodiments, the methodmay further include: removing the corresponding casted layer, if themeasurements yield a difference in chemical composition larger than athreshold value; and pouring new liquid substance into the at least oneof: the first mold portion and the second mold portion.

In some embodiments, pouring the liquid substance into the second moldportion may be in an amount sufficient to form the second casted layerand to compensate for at least one of: shrinkage of the first castedlayer and thickness deviation in the first casted layer.

Some aspects of the invention may be related to an additive castingapparatus. An additive casting apparatus according to embodiments of theinvention may include: a movable dispensing unit in fluid connectionwith a first container containing mold material, the dispensing unitincluding one or more liquid introduction ports for depositing the moldmaterial; a movable pouring unit in fluid connection with at least onesecond container for holding liquid substance, the pouring unitincluding one or more liquid introduction ports for pouring at least oneliquid substance; a build table for holding the deposited mold materialand the poured liquid substance; and a controller configured to: controlthe movable dispensing unit to deposit a first portion of a mold, layerby layer; control the movable pouring unit to pour at least one liquidsubstance into the first portion of the mold to form a first castedlayer; control the movable dispensing unit to deposit a first portion ofa mold, layer by layer, on top of the first portion; and control themovable pouring unit to pour the at least one liquid substance into thesecond portion of the mold to form a second casted layer on top of atleast a portion of the first casted layer.

In some embodiments, the additive casting apparatus may further includea joining unit configured to join the first and second casted layersprior to a deposition of a third mold portion and the pouring of a thirdcasted layer. In some embodiments, the joining unit may be at least oneof: an induction heater, E-beam, a resistance welder, an arc welder, alaser welder, a torch, a gluing device, a cold fusion unit, a magnet formagnetic field flow, an ultrasonic bonding unit and a heater fordiffusion bonding. In some embodiments, the at least one secondcontainer may be a crucible and the liquid substance is one of: a moltenmetal and molten glass. In some embodiments, the at least one secondcontainer may be a tank and the liquid substance is at least one of: apolymer resin or a molten polymer.

In some embodiments, the additive casting apparatus may further includea pre-heating unit for heating each casted layer prior to pouring anadditional casted layer. In some embodiments, the additive castingapparatus may further include one or more surface treatment units fortreating the surface of each casted layer after the solidification andprior to pouring an additional casted layer. In some embodiments, theone or more surface treatment units includes at least one of: amachining device, a grinding device and a polishing device.

In some embodiments, the additive casting apparatus may further includean enclosure filled with protective atmosphere for providing theprotective atmosphere to the casted layers during casting. In someembodiments, the enclosure may include a closed housing accommodating:the movable dispensing unit, the movable casting unit, the build tableand a device configured to provide the protective atmosphere. In someembodiments, the controller may further be configured to: receive athree-dimensional (3D) part model of one or more solid parts, the 3Dpart model is divided into a plurality of casted layers; receive a 3Dmold model of a mold, the mold model is divided into a plurality of moldportions, wherein the mold is designed to provide a desired shape to aliquid substance; control the deposition of the mold portions based onthe mold model; and control the pouring of the casted layers based onthe part model.

In some embodiments, the movable despising unit is configured to move inat least one axis. In some embodiments, the movable pouring unit isconfigured to move in at least one axis. In some embodiments, theadditive casting apparatus may further include the build table and maybe coupled to a movable platform. In some embodiments, the movablepouring unit may be in fluid connection with two containers for holdinga first liquid substances and a second liquid substances, and thecontroller may be configured to: control the movable pouring unit topour the first liquid substance into the first portion of the mold toform a first casted layer; and control the movable pouring unit to pourthe second liquid substance into the second portion of the mold to forma second casted layer.

In some embodiments, the additive casting apparatus may further includeat least one chemical composition sensor configured the measure at leastof: the chemical composition of the liquid substance in the containerand the chemical composition of the casted layers. In some embodiments,the at least one substance composition sensor based on X-ray or laser.

Some additional aspects of the invention may be directed to a castedmetallic part that may include: at least a first casted layer includinga first type of alloy; at least a second casted layer including a secondtype of alloy, joined to the at least first casted layer. In someembodiments, the first and second alloys are different alloys of thesame metallic element. In some embodiments, the thickness of each castedlayer may be at least two orders of magnitude smaller than the perimeterof each casted layer. In some embodiments, the casted metallic mayfurther include a third casted layer joined to at least one secondcasted layer. In some embodiments, the third casted layer may include athird type of alloy of the same metallic element. In some embodiments,the at least a first casted layer may differ from the at least a secondcasted layer also in microstructure.

Some additional aspects of the invention may be directed to a castedmetallic part that may include: at least a first casted layer having afirst predetermined microstructure; and at least a second casted layerhaving a second predetermined microstructure, joined to the at leastfirst casted layer. In some embodiments, the first and secondpredetermined microstructures may differ at least in the average grainsize. In some embodiments, the thickness of each casted layer may be atleast two orders of magnitude smaller than the perimeter of each castedlayer. In some embodiments, the casted metallic may further include athird casted layer joined to at least one second casted layer. In someembodiments, the third casted layer having a third predeterminedmicrostructure.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings in which:

FIG. 1 is an illustration of an additive casting apparatus according tosome embodiments of the invention;

FIG. 2 is a flowchart of a method of additive casting of parts accordingto some embodiments of the invention;

FIGS. 3A and 3B are illustration of an in processes casted part and moldaccording to some embodiments of the invention;

FIG. 4 is an illustration of an in processes casted part and moldaccording to some embodiments of the invention; and

FIG. 5 is a detailed flowchart of a method of additive casting of partsaccording to some embodiments of the invention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, and components have notbeen described in detail so as not to obscure the present invention.

A casting apparatus and method according to embodiments of the inventionmay include producing casted parts layer by layer, by pouring liquidmedium (e.g., a molten metal/alloy, molten glass, a polymer resin, etc.)into mold portions being deposited themselves layer by layer. The liquidmedium may be any liquid material that can solidify when poured into amold, either spontaneously (e.g., solidification of molten martials dueto cool down) or assisted by an additional process (e.g.,polymerization/crosslinking of monomers or a polymer precursor usingheat or ultraviolet (UV) curing).

As used herein, a mold (also known in the art as a shell) may includeany hollow cavity configured to provide a shape to the liquid materialbeing poured into the mold and allowed to solidify. A mold according toembodiments of the invention may be manufactured by printing/depositinglayer by layer of mold material to form different mold portions, asdisclosed herein. As used herein, a mold material may be any materialsuitable for being deposited/printed from a deposition unit and providea shape for a specific liquid material being poured into the mold, afterthe mold deposition. For example, when the liquid material is a moltenpolymer or a polymer resin the mold material may also include a polymer.In another example, when the liquid material is molten metal (e.g.,having a melting temperature of above 500° C.) or molten glass (e.g.,having a melting temperature of above 1000° C.) the mold material mayinclude granular material mixed with a binder and configured to holdmolten substance at elevated temperatures. The granular material mayinclude: ceramic powders (e.g., zirconia, alumina, magnesia, etc.),sand, clay, metallic powders and any combination thereof. In someembodiments, the mold material may further include activation additives.For example, UV absorbing particles, crosslinking agents, heat absorbingparticles and the like.

In order to ensure the bonding between consecutive casted layers ajoining process may be conducted, using any joining method known in theart. The joining method may be selected according to the castedmaterial, for example, two metallic layers may be welded, two glasslayers may be diffusion bonded and two polymeric layers may be gluedand/or crosslinked.

Reference is now made to FIG. 1 which is an illustration of an additivecasting apparatus according to some embodiments of the invention. Suchan additive casting apparatus may allow depositing a plurality of moldportions substantially one on top of the other that may form a singlemold for casting liquid medium. Each mold portion, as deposited, may befilled with liquid substance in order to form a casted layer, prior tothe deposition of an additional mold portion. Thus, forming castedpart(s) made from a plurality of casted layers, being casted one on topof the other. Depositing, each mold portion may include depositing oneor more layers of mold material.

An additive casting apparatus 100 may include a movable dispensing unit130 for depositing the mold material and a movable pouring unit 120 forpouring at least one liquid substance. Additive casting apparatus 100may further include a build table 116 for holding the deposited moldmaterial and the poured liquid substance and a controller 153 configuredto control the controllable components of apparatus 100. In someembodiments, additive casting apparatus 100 may further include a fixedframe 170 for holding at least some of the movable elements of additivecasting apparatus 100. Fixed frame 170 may be stationary.

In some embodiments, movable dispensing unit 130 may include one or moreliquid introduction ports 134 (e.g., nozzles, spouts and the like) forpouring at least one liquid substance. In some embodiments, movabledispensing unit 130 may be in fluid connection and/or may include withat least one first container 132 containing the mold material. In someembodiments, first container 132 may be any tank/cartridge/magazineconfigured to hold the mold material. In some embodiments, firstcontainer 132 may include a stirrer for stirring the mold material infirst container 132 prior to the deposition.

In some embodiments, movable dispensing unit 130 may further include acontrollable valve configured to control the amount of mold materialbeing poured to form each mold layer in each mold portion 112 from oneor more liquid introduction ports 134. In some embodiments, movabledispensing unit 130 may be configured to move in at least one axis(e.g., the X axis as illustrated), for example, when build table 116 maybe coupled to a movable platform configured to move in the at least twoother axes (e.g., the Y and Z axes). In some embodiments, movabledispensing unit 130 may be configured to move in two or three axes. Insome embodiments, movable dispensing unit 130 may be mounted on an X-Ytable configured to move movable dispensing unit 130 to any point overbuild table 116. In some embodiments, build table 116 and movabledispensing unit 130 may be mounted on fixed frame 170 and may each beallowed to relatively move in at least one axis with respect to fixedframe 170. In some embodiments, movable dispensing unit 130 may becontrolled (e.g., by controller 153) to deposit mold portions 112 (e.g.,first, second, third, fourth, etc. portions) layer by layer.

In some embodiments, movable pouring unit 120 may include one or moreliquid introduction ports 124 for pouring at least one liquid substanceinto a respective mold portion 112. Movable pouring unit 120 may be influid connection with at least one second container 122 for holdingliquid substance. In some embodiments, when the liquid substance is oneof: a molten metal, molten alloy and molten glass at least one secondcontainer 122 may be a crucible. The crucible may be made from anymaterial that withstands elevated temperatures. The crucible may includean opening for receiving the molten metal or molten glass (melted in amelting crucible) and at least one exit for providing the melted metalor glass to pouring unit 120. In some embodiments, the crucible may beincluded in pouring unit 120.

In some embodiments, when the liquid substance is at least one of: apolymer resin or a molten polymer, container 124 may be a tank (e.g., ametallic tank) for holding the polymer resin or the molten polymer. Insome embodiments, the tank may include a stirrer (not shown) forstirring the polymer resin. In some embodiments, the tank may beincluded in pouring unit 120.

In some embodiments, movable pouring unit 120 may be in fluid connectionwith two or more containers for holding a first liquid substances and asecond liquid substances. In some embodiments, the first liquidsubstances may have a first chemical composition and the second liquidsubstances may have a second chemical composition, for example, thefirst liquid substance and the second liquid substance may be selectedfrom: two alloys of the same metallic element, two types of glass andtwo types of polymers.

In some embodiments, movable pouring unit 120 may further include acontrollable valve configured to control the amount of liquid substancepoured to form each casted layer 104 from one or more liquidintroduction ports 124. In some embodiments, movable pouring unit 120may be configured to move in at least one axis parallel to the surfaceof build table 116 (e.g., the X axis illustrated), for example, whenbuild table 116 may be coupled to a movable platform and configured tomove in the at least two other axes (e.g., the Y and Z axes). In someembodiments, movable pouring unit 120 may be configured to move in twoor three axes. In some embodiments, movable pouring unit 120 may bemounted on an X-Y table configured to move movable pouring unit 120 toany point over build table 116. In some embodiments, build table 116 andmovable pouring unit 120 may be mounted on fixed frame 170 and may eachbe allowed to move in at least one axis with respect to fixed frame 170.In some embodiments, movable pouring unit 120 may be controlled (e.g.,by controller 153) to pour each casted layer 104 into a correspondingmold portion (e.g., first, second, third, fourth, etc., portions).

As used herein, a casted layer is a layer made from a liquid substancepoured into a mold portion and solidify into a solid casted layer in themold portion. The casted layer may receive its shape from the shape ofthe mold portion. The casted layer may include, a casted polymer, castedmetal/alloy, casted glass and the like. A casted layer according to someembodiments of the invention may be casted (e.g., poured) on top of abuild table, a mold layer, or a previously casted layer, as illustratedin FIG. 1 and discussed with respect to the method of FIG. 2. In someembodiments, the thickness of a typical casted layer may be at least twoorders of magnitude smaller than the perimeter of each casted layer. Aplurality of solidified casted layers 104 one on top of the other mayform a casted part 102.

In some embodiments, additive casting apparatus 100 may further includeat least one sensor 126 for measuring a chemical composition of theliquid substance in first container 122 and/or measuring the chemicalcomposition of casted layer 104. At least one sensor 126 may be coupledto movable pouring unit 120. In some embodiments, a single sensor 126may be assembled such that the sensor may measure both the chemicalcomposition in first container 122 and each casted layer 104. In someembodiments, one or more sensors 126 may include an X-Ray based sensoror a laser-based sensor. It should be appreciated that any other sensorcapable of measuring chemical composition of casted layer 104 may beused.

In some embodiments, additive casting apparatus 100 may further includea joining unit 140 configured to join first and second casted layers 104prior to a deposition of a third mold portion 112 and the pouring of athird casted layer 104. In some embodiments, in order to form a solidpart, consecutive casted layers 104 must be joined together. In someembodiments, joining unit 140 may be one of: an induction heater, aresistance welder, an arc welder, a E-beam unit, an ultrasonic welder, aplasma deposition unit, a laser welder, a torch, a gluing device, a coldfusion unit, a magnet for magnetic field flow, an ultrasonic bondingunit, a heater for diffusion bonding and the like. In some embodiments,the type and number of joining devices 140 may be selected according tothe type of liquid substance being poured. Joining unit 140 may beconfigured to move in at least one axis (e.g., the X axis illustrated).For example, joining unit 140 may be carried/coupled to robotic arm 151capable of moving joining unit 140 to any required point over thesurface a casted layer 104. In another example, joining unit 140 may becoupled to a movable X-Y table.

In some embodiments, additive casting apparatus 100 may further includea pre-heating unit 145 for heating each casted layer 104 prior topouring an additional casted layer 104. In some embodiments, when thecasted liquid substance is molten metals, alloys or glass, in order toreduce the temperature gradient between the already solidified castedlayer and the molten material being poured to form the additional castedlayer, the solidified casted layer may be pre-heated, for example, by anindication heater, or any other suitable heating element (e.g.,filament). Pre-heating unit 145 may be configured to move in at leastone axis (e.g., the X axis as illustrated). For example, Pre-heatingunit 145 may be carried/coupled to robotic arm 151 capable of movingpre-heating unit 145 to any required point over the surface of a castedlayer, such as layer 104. In another example, pre-heating unit 145 maybe coupled to a movable X-Y table. In some embodiments, a movablepre-heating unit 145 may be may be configured to move with respect tofixed arm 170.

In some embodiments, additive casting apparatus 100 may further includeone or more surface treatment units 128. The one or more surfacetreatment units may include at least one of: a machining device, agrinding device, a polishing device, a laser ablation unit, and thelike. For example, the machining device may be included any cutting toolconfigured to at least one of: mill, drill, broach, saw and the like. Insome embodiments, the machining device may be a computer numericalcontrol (CNC) controlling a plurality of cutting tools. In someembodiments, surface treatment units 128 may include a grinding machineand/or a polishing machine for receiving fine and ultrafine surfacefinishing.

In some embodiments, surface treatment units 128 may be configured totreat the surface of each casted layer 104 including both mold andpoured material after the solidification and prior to pouring anadditional casted layer 104. In some embodiments, surface treatmentunits 128 may be configured to treat the inner and/or upper surface ofeach mold portion 112 prior to pouring the corresponding casted layer104, as illustrated and discussed with respect to FIG. 4. As usedherein, the upper surface is the surface parallel to table 116 and innersurface is the surface of the inner walls of the mold portion that maycome in contact with the poured liquid substance. In some embodiments,one or more surface treatment units 128 may be configured to machine theupper surface of both the mold portion and the corresponding castedlayer, prior to depositing of another casted layer, in order to leveland even the height (e.g., thickness) of both the mold portion and thecorresponding casted layer. The leveling may ensure an accuratedeposition and pouring of the following mold portion and casted layer.One or more surface treatment units 128 may be configured to move in atleast one axis (e.g., the X axis as indicated by the illustratedarrows).

In some embodiments, additive casting apparatus 100 may further includea hardening unit (not illustrated) for assisting in the hardening of apolymeric casted layer 104 after pouring, for example, by heating or UVcuring.

In some embodiments, additive casting apparatus 100 may further includean enclosure 160 filled with protective atmosphere for providing theprotective atmosphere to the casted layers during casting. As usedherein a protective atmosphere may include any atmosphere that canprotect the surface of the as casted layer 104 from undesirable chemicalreactions, such as, oxidation and carbonization. The protectiveatmosphere may include, an inert gas such as argon, nitrogen and thelike. The protective atmosphere may include vacuum. In some embodiments,enclosure 160 may include a closed housing accommodating at least:movable dispensing unit 130, movable casting unit 120, build table 116and a device 165 configured to provide the protective atmosphere, forexample, a vacuum pump, an argon source and the like.

In some embodiments, build table 116 may be or may include a surfaceconfigured to hold the deposited mold material and the poured liquidsubstance. Build table 116 may include any suitable material, forexample, metals such as steels, ceramics, such as, alumina and the like.In some embodiments, build table 116 may include more than one type ofmaterial (for example, a metal and a ceramic) when the first moldportion 112 is to be deposited on a ceramic surface and the first castedlayer 104 is to be poured on a metallic surface.

In some embodiments, build table 116 may be movable and may beconfigured to move in at least one axis, for example, the three axesindicated by the illustrated arrows. In some embodiments, build table116 may be configured to rotate around the vertical axis. Build table116 may be coupled to a movable platform, such as an x-y table and thelike.

In some embodiments, controller 153 may include any processing unit,such as, processor 155 configured to execute methods, codes andinstructions according to embodiments of the present invention. Themethods, codes and instructions may be stored in non-transitory storage157, for example, instructions to control various controllablecomponents of casting apparatus 100 (e.g., movable dispensing unit 130,movable pouring unit 120, build table 116, joining unit 140,pre-treatment unit 145 and the like). Storage 157 may further includeany data related to the operation of casting device 100, for example, 3Dmodels of parts and/or molds. In some embodiments, controller 153 may beconfigured to: control movable dispensing unit 130 to deposit a firstportion of a mold, layer by layer; control movable pouring unit 120 topour at least one liquid substance into the first portion of the mold toform a first casted layer; control movable dispensing unit 130 todeposit a first portion of a mold, layer by layer, on top of the firstportion; and control movable pouring unit 120 to pour the at least oneliquid substance into the second portion of the mold to form a secondcasted layer on top of at least a portion of the first casted layer. Insome embodiments, controller 153 may control movable dispensing unit 130and movable pouring unit 120 to deposit and pour a plurality of moldportions and the corresponding casted layers, as discussed with respectto the methods of FIGS. 2 and 5.

Reference is now made to FIG. 2 which is a flowchart of a method ofadditive casting of parts according to some embodiments of theinvention. The method of FIG. 2 may be performed by additive castingapparatus 100 under the control of controller 153. In some embodiments,instructions to perform at least some of the steps of the method of FIG.2 may be stored in storage 157. In some embodiments, a 3D model of oneor more parts to be casted may be received, in step 220. The 3D partmodel may be received by controller 153, via I/O unit 159, for example,from any computer aided design (CAD) software. Controller 153 may thendivide the 3D part model into a plurality of casted layers, for example,layers 104, 104 a, 104 b in FIG. 1 layer 204 in FIGS. 3A and 3B and 304in FIG. 4.

In some embodiments, a 3D model of the mold may be received, in step222. The 3D mold model may be received by controller 153, via I/O unit159, for example, from any computer added design (CAD) software. In someembodiments, the 3D model may be generated, in step 222, based forexample, on the 3D part model. Controller 153 may use any softwaremodule to generate a 3D mold model designed to provide a desired shapeto a liquid substance, as to form the final casted part(s). In someembodiments, the 3D mold model may be divided into a plurality of moldportions (e.g., shells), for example, mold portions 108 and 112illustrated in FIG. 1, portions 212, 213 and 215 illustrated in FIGS. 3Aand 3B and portions 312 and 313 illustrated in FIG. 4. In someembodiments, each mold portion may further be divided into one or moremold layers, such that each mold portion may include one or more (e.g.,two or more) deposited mold layers.

In some embodiments, a first portion of a mold may be deposited on abuild table, layer by layer, in step 224. For example, first portion 212illustrated in FIGS. 3A and 3B or first portion 312 illustrated in FIG.4 may be deposited by movable dispensing unit 130. Controller 153 maycontrol movable dispensing unit 130 to deposit the mold materialaccording to the division of the mold model. In some embodiments,controller 153 may control movable dispensing unit 130 to deposit themold material in specific locations on build table 116 by controllingone or more liquid introduction ports 134 to drop mold material whenmovable dispensing unit 130 reaches each of the specific locations.Controller 153 may control at least one of movable dispensing unit 130and build table 116 to move with respect to one another as to positionmovable dispensing unit 130 at the specific location. At the end of thedeposition, the mold portion may form a shape having closed walls (e.g.,a ring, an open box, etc.) configured to accommodate a liquid substance.

In some embodiments, the method may include depositing an initial moldlayer (e.g., portions 108 illustrated in FIG. 1, 211 illustrated inFIGS. 3A and 3B and 311 illustrated in FIG. 3) prior to the depositionof the first mold portion as to have a complete coverage of the buildtable at the bottom of the first mold portion.

In some embodiments, liquid substance may be poured into the firstportion of the mold to form a first casted layer, in step 226. Forexample, molten metal, molten glass, polymer resin etc. may be pouredfrom movable pouring unit 120 into a volume formed by the walls of moldportion 212 to form casted layer 204, as illustrated in FIGS. 3A and 3B.In some embodiments, movable pouring unit 120 may continuously pour theliquid substance while moving along the surface of build table 116. Insome embodiments, the amount of liquid substance being poured may becalculated, by controller 153, according to the volume formed by thewalls of mold portion 212 and the expected shrinkage of the liquidsubstance during the solidification. Controller 153 may control at leastone of movable pouring unit 120 and build table 116 to move with respectto one another. In some embodiments, at least a portion of the firstcasted layer may solidify, is step 228. For example, molten material maybe at least partially solidified due to temperature dropping starting,for example, from the mold portions' walls and inwards. In yet anotherexample, polymer resin (e.g., a precursor or a mixture of monomers) maypolymerized, cured or crystallized, either spontaneously or with the aidto external energy source, such as UV lamp.

In some embodiments, a second portion of the mold may be deposited,layer by layer, on top of the first portion, in step 230. For example,second mold portion 213 may be deposited on top of first portion 212,according to the divided 3D mold model, as illustrated in FIGS. 3A and3B. The deposition of second mold portion 213 may be substantially thesame as the deposition of first mold portion 212 discussed in step 224.In some embodiments, a third mold portion 215 may be deposited on top ofsecond mold portion 213, as illustrated in FIG. 215.

In some embodiments, the mold material may be deposited, layer by layer,in order to form support structures in the mold. Such a supportstructure may include one or more elements for overhanging castedlayers. For example, at least one mold portions may include one or moreprotrusions that may form support for casted layers poured above theprotrusions.

In some embodiments, the inner walls of each mold portion may undergosurface treatment prior to the pouring of an additional casted layer, instep 232. In some embodiments, the surface treatment may include atleast one of: machining, grinding, polishing and the like, for example,by surface treatment unit 128. For example, a 90° mill 206, illustratedin FIGS. 3A and 3B may mill the walls of second mold portion 213 (andthird mold portion 215) as to attain a more precise and smooth edge. Inyet another example, a slope may be provided to the walls of moldportion 313, illustrated in FIG. 4, by an angled end mill 306. In someembodiments, the excess material machined (e.g., milled) may be removedfrom the corresponding mold portion, as not to be mixed with the liquidsubstance to be poured into the mold portion.

In some embodiments, liquid substance may be poured into the secondportion of the mold to form a second casted layer, on top of at least aportion of the first casted layer, in step 234. The pouring of thesecond casted layer may be substantially the same as the pouring of thefirst casted layer. In some embodiments, the second casted layer may belet to at least partially solidify, in step 236. In some embodiments, atleast some of steps 224-236 may be repeated until the entire 3D part(e.g., part 102 illustrated in FIG. 1) is additively casted by pouring aplurality of casted layers. In some embodiments, pouring the liquidsubstance into the second mold portion may be in an amount sufficient toform the second casted layer and to compensate for at least one of:shrinkage of the first casted layer and thickness deviation in the firstcasted layer. For example, controller 153 may control pouring unit 120to pour more liquid substance than the amount required to form thesecond casted layer, according to the received 3D model. The addedliquid substance may be determined as to compensate for deficienciesformed in the first casted layer.

In some embodiments, the first and second casted layers may be joinedprior to the pouring of a third casted layer, in step 238. In someembodiments, when casting different casted layers, a thin film may beformed on the free upper surface of each casted layer. When pouring thefollowing layer, the thin film may form a boundary between two adjacentcasted layers and may reduce the bonding strength between the layers.Accordingly, in order to increase the bonding strength, an additionaljoining/bonding operation may be conducted. For example, if the liquidsubstance is molten metals/alloys the joining may include melting atleast a portion of the interface between the first and second castedlayers. The melting may be conducted by, for example, heating/treatingat least a portion of an upper surface of the second casted layer, suchthat a temperature higher than the melting point of the casted substancemay be formed in the interface between the first and second castedlayers. The heating/treating may be with one of: an induction heater, aresistance welder, a laser, a welding arc, a torch, cold fusion,magnetic field flow and the like. In another example, if the liquidsubstance is molten glass, molten polymer or a polymer resin the joiningmay include at least one of: gluing, ultrasonic bonding, diffusionbonding, heat curing, UV curing and the like.

In some embodiments, each casted layer may be pre-heated prior to thepouring of an additional casted layer, in step 240. In some embodiments,the pre-heating is conducted in order to minimize the thermal shocksthat may cause macro and micro defects, such as cracks, in the castedlayers during the pouring of the additional casted layer. In someembodiments, the previously casted layer may be preheated, for example,to 600-700° C. prior to pouring molten metal or molten glass at1000-1300° C., thus reducing thermal shock.

In some embodiments, a surface treatment may be provided to each castedlayer after the solidification and prior to the pouring of an additionalcasted layer, in step 242. The surface treatment may include removing anupper film (e.g., a thin oxidized layer) from the casted layer and mayalso include leveling the mold portion. In such case the removing of theupper film may cause leveling or evening the first casted layer and thefirst mold portion to be in the same level prior to the deposition ofthe second mold portion. The leveling may allow more accurate depositionof the second mold portion. In some embodiments, the surface treatmentmay include at least one of: machining, grinding, polishing and laserablation.

In some embodiments, pouring the third and fourth casted layers maycause a reheating to some extant an already fully solidified lowercasted layer. The reheating may cause an, in situ, annealing process inthe first casted layer result in at least partial stress relief of thefirst casted layer.

In some embodiments, the first casted layer (e.g., layer 104 a) may becasted by pouring a first liquid substance having a first chemicalcomposition; and the second casted layer (e.g., layer 104 b) may becasted by pouring a second liquid substance having a second chemicalcomposition. In some embodiments, the first liquid substance and thesecond liquid substance may be selected from: two alloys of the samemetallic element, two types of glass (e.g., colored by two differentpigments) and two types of polymers, as to ensure the bonding/joining ofthe first and second casted layers to each other. For example, the firstcasted layer may include a first type of grey cast iron and the secondcasted layer may include ductile iron, when cast part 102 may requiregrater hardness at one part while having ductility and shock absorbingability in another part.

In some embodiments, in addition to controlling the chemical compositionalso the microstructure of the first and second casted layers (and anyother layer in part 102) may be controlled to be different from eachother. For example, by selecting different pre-heating temperature to beprovided to the previously poured casted layer, the microstructure maybe altered. The lower the selected pre-heating temperature is the finerthe microstructure of the poured layer will be. In some embodiments,additives added to the first and second liquid substances may also alterthe microstructure. Therefore, the first liquid substance and the secondliquid substance may differ in at least one of: the amount and the typeof additives that are configured to at least: evaporate and decomposeduring casting.

In some embodiments, the method of FIG. 2 may further include measuringa chemical composition of the liquid substance in the first containerprior to pouring the liquid substance into at least one of: the firstmold portion and the second mold portion; and measuring the chemicalcomposition of the corresponding casted layer. For example, one or moresensors 126 may measure the chemical composition of the liquid substancein first container 122 and then measure the chemical composition in thelast casted layer. In some embodiments, the sensor may send themeasurements to controller 153 and the controller may compare themeasurements. In some embodiments, if the measurements yield adifference in chemical composition larger than a threshold value (e.g.,due to oxidation of the casted layer) the measured casted layer may beremoved, and a new liquid substance may be poured into the at least oneof: the first mold portion and the second mold portion. For example,controller 153 may control surface treatment unit 128 to remove (e.g.,by milling) an entire casted layer and control movable pouring unit 120to pour a new casted layer to replace the removed one.

In some embodiments, the method of FIG. 2 may further include removingall the mold portions at the ending of the solidification of the lastcasted layer. The removing of the mold portions may be conductedaccording to any known method, for example, by mechanical means orchemical means.

Referring back to FIG. 1 and cast part 102, in some embodiments, castpart 102 may be a metallic part including: at least a first casted layer104 a and at least one second casted layer 104 b. In some embodiments,at least a first casted layer 104 a may include a first type of alloyand at least a second casted layer 104 b may include a second type ofalloy. In some embodiments, the first and second alloys may be differentalloys of the same metallic element. For example, first casted layer 104a may include aluminum A355 and second casted layer 104 a may includealuminum A356. In yet another example, first casted layer 104 a mayinclude grey cast iron and second casted layer 104 a may include ductileiron. In some embodiments, cast metallic part 102 may include a thirdcasted layer 104 having a third type of alloy of the same metallicelement.

In some embodiments, all casted layers 104 may be casted from the samealloy however, at least a first casted layer 104 a may include a firstpredetermined microstructure and at least a second casted layer 104 bmay include a second predetermined microstructure. There are severalmethods known in the art for altering the microstructure of variousalloys, during the solidification processes. The methods are based oncontrolling the nucleation process, in which small grain nuclei areformed in the melted metal and then grow into the final grain. There aretwo main approaches: 1) controlling the over-cooling thus controllingthe energetic deriving force for creating the nuclei and 2) addingnucleation centers (e.g., powders that includes compounds that may useas nucleation centers) to the melt prior to pouring the melt into themold.

In some embodiments, the cooling rate of the casted layer can becontrolled by providing different pre-heating temperature to thepreviously casted layer. For example, cast part 102 may be casted fromaluminum A356, however, first casted layer 104 a may have larger grainsize (e.g., crystal size) than second casted layer 104 b. The differentgrain size may be archived by providing different pre-heating treatmentto each layer, as disclosed herein above. In another example, cast part102 may be casted from grey cast iron, however, first casted layer 104 amay have larger graphite flakes than second casted layer 104 b. Thelarger the temperature difference between the molten metal being pouredand the substrate (e.g., the former casted layer) the greater is thedriving force for creating nuclei, thus the larger is the number ofnuclei formed and the finer the final microstructure may be.

In some embodiments, the microstructure may be controlled by the amountof nucleation centers provided to the melt in each layer. For example,ZrO₂ particles may be added at two different amounts (e.g., 0.5 wt. % tolayer 104 a and 1.7 wt. % to layer 104 b) to SP steel in order to refinethe microstructure. The larger the amount the of ZrO₂ particles thelarger the amount of nucleation sites and the finer is themicrostructure. In some embodiments, at least one first casted layer 104a and at least one second casted layer 104 b may differ both in the typeof alloy and the microstructure.

In some embodiments, at least a first casted layer 104 a and at least asecond casted layer 104 b may be joined together. For example, the atleast a first casted layer 104 a and at least a second casted layer 104b may be welded to each other, diffusion bonded to each other and thelike as to form a solid metallic part. In some embodiments, themicrostructure of the joined areas may be distinguished from the rest ofthe cast part, a phenomenon known in the art as heat affected zone(HAZ). In some embodiments, if the casted layers have a thicknesssmaller than the HAZ, then all casted layers may have a HAZmicrostructure and the joined areas may not be distinguishable.

In some embodiments, the thickness of each casted layer 104, 104 a, 104b may be at least two orders of magnitude smaller than the perimeter ofeach casted layer.

Reference is now made to FIG. 5 which is a detailed flowchart of amethod of additive casting of parts according to some embodiments of theinvention. In some embodiments, the method steps may be performed bycontroller 153 directing an additive casting apparatus 403. In someembodiments, additive casting apparatus (e.g., a 3-D printer) 403 mayinclude at least some of the components of additive casting apparatus100, illustrated in FIG. 1.

In some embodiments, the process may start at step 400, when a 3D moldmodel 405 and a 3D part model 407 may be stored in storage 157 ofcontroller 153. In some embodiments, 3D mold model 405 and a 3D partmodel 407 may be divided to a plurality of mold portions and acorresponding plurality of casted layers to be included in a layer buildmap set 409. For example, for illustrative purposes as including castedlayer and the corresponding mold portions build maps 409-1, 409-2, . . ., 409-N, for a 3D printed part that is poured using N layers. Forpurposes of illustration and discussion, a typical casted layer and moldportion build map 409-C may include casted layer and mold portion data411, that may contain a layer/portion thickness parameter 413, a numberof mold layers 415 within each mold portion, and edge profile data 417.In the discussions of layer fabrication, build map 409-C may be taken asthe “current” layer build map during the 3D additive casting process.

In some embodiments, edge profile data 417 may specify, for example, theshape and angle of the mold walls such as illustrated in FIG. 3A andFIG. 4. In some embodiments, edge profile data 417 may also containinformation regarding the sequencing of surface finishing operations,such as illustrated and discussed in FIG. 3B, such that two moldportions (e.g., mold portion 213 and mold portion 215) may be finishedsimultaneously by end mill 206 (as opposed to finishing portion 213before depositing portions 215).

In some embodiments, an additional data stored in readable memoryaccessible to controller 153 may include material parameters 421, forexample, the mold material parameters 423 and the liquid substanceparameters 425. Material parameters may include specifications andcharacteristics of the materials, including at least one of: physicalproperties, chemical compositions and other data necessary to carry outmethod steps. In a non-limiting example, for a mold material that may beheated to be hardened, mold material parameters 423 may include thetemperature and time for hardening. In some embodiments, if thetemperature and time derived from the thickness of the mold walls, thenmold material parameters 423 may include a formula or lookup table fromwhich the parameters could be derived from the thickness.

Additive casting of a 3D part (e.g., part 102) may begin at step 431,and may be followed by the deposition of mold layer to form the firstmold portion (e.g., portion 112), at deposition loop 433. The depositionof a new mold portion may be initialized in an initialization step 435.Initialization steps may include, for example, a selection of theappropriate mold portion form build map set 409. For example, the firstmold portion may be deposited according to layer build map 409-1, thesecond mold portion may be deposited according to build map 409-2, andso forth, up to the casting of the final casted layer/mold portion,according to build map 409-N (for N layers). In a non-limiting example,build table 116 may be initialized in position for the mold portion tobe properly deposited and/or the liquid substance be properly poured.

In some embodiments, the mold portion may be deposited, in step 437. Forexample, mold material may be laid layer by layer (e.g., from movabledispensing unit 130) according to the mold 3D model 405 data in thecurrent build map 409-C (e.g., the current layer in the build map ineffect), such that the mold material delineates a region where liquidsubstance is to be subsequently poured into (e.g., from movable pouringunit 120). In some embodiments, the mold material may be deposited bymovable dispensing unit 130, positioned and moved by robotic arm 151, asdirected by controller 153.

In some embodiments, at step 439, it may be determined whether a furthermold layers should be laid on top of the former mold layer already laidin deposition step 437. The deposition of an additional mold layer atthis point may be determined according to the 3D model of the moldportion included in build map 409-C. If a further mold layer is to bedeposited, then deposition step 437 may be repeated, as many times asrequired by build map 409-C in order to complete the corresponding moldportion.

In some embodiments, when no further mold layer is to be deposited aftermold deposition step 437, the method may include a mold hardening step441, to harden all the layers of the mold portion that have beendeposited. In some embodiments, the hardening step may be selectedaccording to the mold material parameters. Some mold materials may notrequire hardening at all. Hardening may be accomplished by any methodknown in the art, such as UV curing, heating and the like. In someembodiments, the mold material may spontaneously harden over a period oftime. Thus, according to this embodiment mold hardening step 441 mayinclude waiting an appropriate amount of time after the deposition ofthe mold material. Moreover, according to this embodiment, the waitingtime may be included in mold material parameters 423, such as by avalue, a table, and/or a formula.

In some embodiments, in step 443, it is determined whether a furthermold layers may be laid on top of the mold material already deposited indeposition step 437 and optionally hardened in mold hardening step 441.The deposition of further mold layer/portions at this point may bedetermined based on build map 409-C. If a further mold layer is to bedeposited, then deposition step 437 may be repeated to form the moldportion.

In some embodiments, if no further mold layers are to be deposited, thena mold surface finishing step 445 may be performed. In some embodiments,the surface of the walls of the hardened mold may be machined, grindedand/or polished. Mold surface finishing may include surface treatment ofeither the top surface of the walls of mold portion, or the innersurface of the mold portion, which delineates the part surface to besubsequently formed. Mold surface finishing may be accomplished by oneor more of the means previously described herein.

In some embodiments, in pouring step 451, liquid substance may be pouredaccording to the 3D part model 407 data of current layer build map409-C. In some embodiments, the amount of liquid substance to be pouredmay be determined such that, the liquid substance fills the regiondelineated by the mold portion. In some embodiments, liquid substancemay be poured by movable pouring unit 120, for example, positioned andmoved by robotic arm 151 as directed by controller 153.

In some embodiments, the amount of liquid substance poured into thecorresponding mold portion may be determined based on liquid substanceparameters 425, for example, the amount of expected shrinkage of theliquid substance during the solidification. The amount may include anadditional computation according to volumetric factors such astemperature changes, phase changes, and the like, to allow forexpansion, shrinkage, density changes, and so forth.

In some embodiments, in solidification step 453, the poured liquid buildtable may at least partially be solidified into casted layer.

In some embodiments, if there is a previously-consolidated casted layerbeneath the present casted layer, the solidification process may bondthe present casted layer to the previously-poured casted layer, so thatboth casted layers may be part of the same solid part. In someembodiments, an additional joining process may be conducted in order tojoin the two adjacent casted layers, as disclosed herein above.

In some embodiments, in casted layer surface finishing step 455, the topsurface of the casted layer may be treated to have a smooth and levelsurface of a desired thickness in preparation for the next casted layer,if any, such as by steps previously discussed.

In some embodiments, casted layer pouring loop end 457 may be reached,and at a decision may be taken in step 459 by, for example, controller153 checks if there is a subsequent casted layer to be fabricated. Ifthere is a subsequent casted layer, casted layer pouring loop 433-457may be repeated, using the next casted layer build map data from buildmap data set 409.

In some embodiments, if no subsequent casted layer is to be poured, the3D additive casting may be terminated at a point 461, and all moldportions forming the mold may be removed in removal step 463. In variousembodiments of the present invention, the mold removal may be doneaccording to any known method, for example, chemically, by use of asolution that removes the mold without affecting the 3D casted partwithin the mold. In other embodiments, the mold may be mechanicallyremoved.

In some embodiments, a number of new layers that still need to bepoured/deposited may be determined in step 401, given the number of newcasted layers 401, a decision may be made in step 459, to repeat steps433 through 457.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

1.-20. (canceled)
 21. A system for casting an object by additivelyproducing layers of the object using a build table, the systemcomprising: a mold system for constructing multiple mold layers over thebuild table, the multiple mold layers delineating multiple objectlayers; a positionable object material dispenser, moveable about an areaof the build table, for depositing object material into an object layerdefined by a mold layer, the object material dispenser comprising: amolten metal system; and a holder for holding the molten metal system;and one or more heating units moveable about the area of the buildtable; wherein, the positionable object material dispenser moves whiledepositing a current object layer over a previous object layer, ofmolten metal, and the one or more heating units configured for at leastone of: a) a pre-heating process including heating at least a portion ofa previous object layer prior to the deposition of the object materialof the current object layer, and b) a post heating process includingheating at least a portion of the current object layer, and wherein aconsecutive mold layer is constructed after the deposition of thecurrent object layer is complete.
 22. The system of claim 21, whereinthe positionable object material dispenser comprises a holder heater incommunication with the holder, for heating the molten metal in theholder.
 23. The system of claim 21, additionally comprising: acontroller for controlling the moveable heater for the pre-heating andthe post heating processes.
 24. The system of claim 23, wherein thecontroller controls the one or more heating units during the pre-heatingprocess to heat the at least a portion of the previous object layer to atemperature where a temperature gradient with the current object layerupon its being deposited over the previous object layer is reduced. 25.The system of claim 23, wherein the controller controls the one or moreheating units in the one or both of preheating and post heatingprocesses to affect solidification parameters of a melt pool constitutedby the preheating process on at least a portion of the previous objectlayer prior to the deposition of the current object layer, and the postheating process including heating at least a portion of the currentobject layer.
 26. The system of claim 23, wherein the controllercontrols the one or more heating units during the post heating processsuch that heating at least a portion of the current object layer is at atemperature sufficient to join the at least the heated portion of thecurrent object layer to a corresponding portion of the previous objectlayer.
 27. The system of claim 21, additionally comprising: a threedimensional (3D) system for providing relative movement between thebuild table and the positionable object material dispenser in adirection perpendicular to a build plane defined by the build table, andwherein the relative movement between the build table and thepositionable object material dispenser is provided after the depositionof the current object layer is complete and before constructingconsecutive mold layer.
 28. The system of claim 21, additionallycomprising: a controller for controlling the positionable objectmaterial dispenser during depositing of the previous and current objectlayers.
 29. The system of claim 21, wherein the one or more heatingunits include a preheating unit and a joining unit.
 30. The system ofclaim 21, wherein the mold system and the positionable object materialdispenser operate by following at least one build plan.
 31. The systemof claim 21 wherein the mold system is to use mold material made ofceramic powder mixed with binders and metal powder in a paste form andwherein the mold layers receiving the object material is at a stateselected from a group consisting of a green state, a fully cured stateand a partially sintered state.
 32. A method for casting an object byadditively producing layers of the object using a build table, themethod comprising, for a plurality of layers: constructing multiple moldlayers on the build table, the mold layers delineating multiple objectlayers; moving a positionable object material dispenser including moltenmetal, about an area of the build table, for depositing the molten metalinto the object layers defined by a mold structure; and depositing, bythe object material dispenser, of molten metal, into the object layer,and performing at least one of a) a preheating process including heatingat least a portion of a previous object layer prior to the deposition ofa current object layer, and b) a post heating process including heatingat least a portion of the current object layer, wherein a consecutivemold layer is constructed after the deposition of the current objectlayer is complete.
 33. The method of claim 32, wherein the preheatingprocess additionally comprises: heating the at least a portion of theprevious object layer to a temperature where a temperature gradient withthe current layer upon its being deposited over the previous objectlayer is reduced.
 34. The method of claim 32, additionally comprising:providing one or more positionable heating units during the at leastpreheating and post heating processes to affect solidificationparameters of a melt pool constituted by the preheating process on atleast a portion of the previous object layer prior to the deposition ofthe current object layer, and the post heating process including heatingat least a portion of the current object layer.
 35. The method of claim32, wherein the post heating process includes heating at least a portionof the current layer is at a temperature sufficient to join the at leastthe heated portion of the current object layer to a correspondingportion of the previous object layer.
 36. The method of claim 32,wherein the mold structure and the object layers are made in accordancewith at least one build plan.
 37. The method of claim 32, additionallycomprising: adding nucleating agents to the molten metal, prior to thedepositing of the molten metal into the object layers to control amicrostructure of the deposited object layer.
 38. The method of claim 32wherein the constructing of multiple mold layers uses mold material madeof ceramic powder mixed with binders and metal powder in a paste formand wherein the mold layers receiving the object material is at a stateselected from a group consisting of a green state, a fully cured stateand a partially sintered state.
 39. The method of claim 32 wherein theone or more mold layers are hardened by heating the one or more moldlayers.
 40. The method of claim 32 further comprising providing relativemovement between the build table and the positionable object materialdispenser in a direction perpendicular to a build plane defined by thebuild table, wherein the relative movement between the build table andthe positionable object material dispenser is provided after thedeposition of the current object layer is complete and before theconstruction of the consecutive mold layer.